$$A=\{x\in\mathbb{N}|x<5\}; B=\{x\in\mathbb{N}^{*}|x<5\}$$
$\left\{\begin{matrix}x=\frac{A}{eN}\text{, }&N\neq 0\\x\in \mathrm{C}\text{, }&A=0\text{ and }N=0\end{matrix}\right.$
$\left\{\begin{matrix}x=\frac{A}{eN}\text{, }&N\neq 0\\x\in \mathrm{R}\text{, }&A=0\text{ and }N=0\end{matrix}\right.$
